This is one of the Radio Shack wattmeters that was very popular in the 1970's and 1980's. It is an average reading meter, and fairly accurate on 160-10 meters. This was a barn find, was pretty dirty, and had a bad modulation meter. I had another meter of the same dimensions, so I swapped the meter face and subbed it into the housing. The mods shown on the marked up schematic convert this to a passive peak reading meter, similar to the Daiwa, Palomar, earlier MFJ, PDC, etc. No battery is required, and it really enhances it's use when tuning amps and transmitters for peak power...
